hi there,i have some problems coming up with an idea how to demonstrate optical properties of an ellipse in openGL.I managed to draw an ellipse to represent the case when there's only one reflection.As you know,a ray is coming out of one focus and has to go through the other one.Any ideas how it could be done for lets say n reflections aka more than two rays.it should look something like this:
After one reflection :http://www.mathwarehouse.com/ellipse/images/formul-focus.gif
http://www.mathwords.com/f/f_assets/f23.gif

After more reflections:
http://bdaugherty.tripod.com/moon/images/ellipse_focus2focus.gif

AND THIS IS MY CODE FOR DRAWING THE ELLIPSE AND THE CASE WHEN THERES ONE REFLECTION(2 rays):
glBegin(GL_POINTS);/*drawing an ellipse*/